The present invention generally relates to an electron emitting device and, more particularly, to a field emission display device and a method of operating the same.
In recent years, flat-panel display devices have been developed and widely used in electronic applications. Examples of flat-panel display devices include the liquid crystal display (“LCD”), plasma display panel (“PDP”) and field emission display (“FED”) devices. FEDs have received considerable attention as a next generation display device having the advantages of LCDs and PDPs. FEDs, which operate on the principle of field emission of electrons from microscopic tips, are known to be capable of overcoming some of the limitations and provides significant advantages over conventional LCDs and PDPs. For example, FEDs have higher contrast ratios, wider viewing angles, higher maximum brightness, lower power consumption, shorter response times and broader operating temperature ranges compared to conventional LCDs and PDPs. Consequently, FEDs are used in a wide variety of applications ranging from home televisions to industrial equipment and computers.
With the property of self-luminescence, an FED may function to serve as an independent light source rather than a display device. The principle of field emission of electrons is briefly discussed by reference to FIG. 1. FIG. 1 is a schematic diagram of a conventional field emission display (“FED”) device 10. Referring to FIG. 1, FED device 10 includes a cathode 12, emitters 13 formed on cathode 12, an anode 14, a phosphor layer 16 formed on a surface (not numbered) of anode 14, and spacers 18. Emitters 13 emit electrons, which are accelerated in an electrical field established between cathode 12 and anode 14 toward phosphor layer 16. The direction of the electrical field is substantially in parallel to the normal direction of cathode 12 or anode 14. Phosphor layer 16 provides luminescence when the emitted electrons collide with phosphor particles. Light provided from phosphor layer 16 transmits through anode 14 to a display device (not shown), for example, an LCD device. Spacers 18 are disposed between cathode 12 and anode 14 for maintaining a predetermined spacing therebetween. Spacers 18 may be affixed to cathode 12 and anode 14 by a glass fit sealant. The inner space defined by cathode 12, anode 14 and spacers 18 is required to be maintained at a vacuum state to ensure continued accurate emission of electrons.
The conventional FED device 10 may have the following disadvantages. The property of field emission of FED device 10 is highly sensitive to the distance between cathode 12 and anode 14. The distance must be precisely controlled with a tolerance in the order of micrometer (μm), which hinders FED device 10 from size upgrades and renders uniform luminescence from FED device 10 difficult. Furthermore, as an element in the optical path, anode 14 may attenuate or even block light provided from phosphor layer 16. To avoid such a risk, anode 14 often employs a transparent material such as indium tin oxide (“ITO”). The transparent material is usually expensive relative to the overall cost of FED device 10. The above-mentioned disadvantages, including the relatively small tolerance in distance control and the cost inefficiency in the use of a transparent anode, render it difficult for FED device 10 to be market available.